Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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269 FXUS66 KPDT 071607 RRA AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 828 AM PDT Tue May 7 2024 .UPDATE...A broad trough remains over the area though it is rapidly moving off to the east while a ridge builds offshore. A weak wave that brought snow to the mountains is also departing but radar shows some showers continuing over the Blue Mountains. The overnight shift extended the Winter Weather Advisory for the Northern Blue Mountains to noon. Will keep that for now but trends are downward and may expire it early. Winds in the Kittitas Valley are increasing and model guidance is confident that the current wind advisory through 11 PM tonight is valid. Will keep that in effect as well. Changes to the current forecast were minimal but did adjust POPs over the eastern mountains slightly and also adjusted a few temperatures today a degree or two upward. Forecast update already out. Perry/83 && .PREV DISCUSSION... /issued 459 AM PDT Tue May 7 2024/ UPDATE...After reviewing web cams and latest radar, it was decided to extend the Winter Weather Advisory for the east slopes of the Oregon Cascades and the northern Blue Mtns until noon today. Web cams show steady snow in several locations, and WSR-88D has shown little decrease in the shower activity. Additional accumulations up to 3 inches are forecast for this morning. PREV DISCUSSION... /issued 408 AM PDT Tue May 7 2024/ SHORT TERM...Today through Thursday night...The winter event for the mountains is coming to an end, although winds will remain a concern for some of the lower elevations. The longwave trough is shifting eastward in response to an upper ridge building along the coast, and this will provide a northwest flow aloft today and a drier northerly flow aloft tonight. Current winter weather advisories for the east slopes of the OR Cascades and the northern Blue Mtns will be allowed to expire at 5 AM. However, there will continue to be scattered orographic mountain snow showers over the northern Blues through the morning hours that will bring an additional inch or two of snow above 5000 feet. The 10:1 ratio from the HREF shows around 80% chance of at least 1" but only 20% for 2" or more in the Tollgate and Ski Bluewood areas. The WA/OR Cascades will also observe scattered light snow showers, mainly on the western slopes and in far northwest Kittitas County associated with the Puget Sound Convergence Zone in the northwest flow aloft. Winds are locally breezy early this morning, and it will be another breezy to windy day today. Surface gradients will be tight for the next 18-24 hours, and surface winds won`t decouple from winds aloft until Wednesday morning. A Wind Advisory is in effect for the Kittitas Valley from 8 AM to 11 PM today. NBM and HREF both indicate around a 75% probability for gusts greater than 45 mph and 25-35% for gusts greater than 50 mph at ELN (less than 20% for greater than 55 mph gusts). A tight cross-Cascade gradient will also result in localized wind gusts 35-45 mph through the Cascade gaps and the eastern Columbia River Gorge. It will be chilly tonight under a dry northerly flow aloft, but breezy winds this evening and a southwest surface gradient through the night will keep lows from falling below freezing in the areas that normally are in growing season--the Lower Columbia Basin and surrounding valleys. Temperatures are forecast to fall into the mid to upper 30s in these area, and there will be patchy frost but not a hard freeze. Other locations will observe lows tonight in the 20s to lower 30s. A warming trend begins Wednesday. Temperatures will be slow to warm at the start as the ridge remains to the west, leaving eastern WA/OR under a northeast flow aloft. A rex block begins to form Thursday, and the upper ridge will strengthen over the PacNW. Wister/85 LONG TERM...Friday through Tuesday...A quiet and dry period is in store for the extended period with POPS less than 15% through Tuesday. The latest GEFS ensemble shows an upper ridge over the region through Saturday which gradually transitions to flat westerly flow Monday and Tuesday. The GFS has a more pronounced shortwave trough moving across the Pacific Northwest on Monday and Monday night but this is not supported by the ensemble clusters. It will be warm Friday with high temperatures 75-85 in the lower elevations, and even warmer on Saturday with highs 83-93 across the lowlands. The NBM probabilities of 90+ degree temperatures peak on Saturday at 30-70% across the Columbia Basin and Yakima Valley. As the ridge flattens Sunday and the flow becomes more westerly a weak cold front will move across the area. This will begin a slight cooling trend and also cause an increase in west winds through the Cascade gaps. The upper bound of the winds will be limited by the absence of strong low to mid level jets. The latest NBM is forecasting peak wind gusts at KELN of 31 mph on Sunday and 33 mph on Monday. At KDLS the peak wind gusts are forecast to be 29 mph both Sunday and Monday. High temperatures will cool to the mid 70s to mid 80s in the lower elevations for Monday and Tuesday. With the warm weather the recent snow in the mountains will melt and will contribute to some rises on area rivers. Significant flooding is not forecast at this time but the current forecast from the Northwest RFC has the Naches River near Cliffdell reaching action stage early Saturday morning. 78 && .AVIATION...12Z TAFS...VFR conditions will prevail through the period. SCT-BKN clouds at 040-070 AGL and some mid clouds above today with a clearing trend this evening becoming SKC tonight. Winds will increase this morning and become 15-20 kt sustained and gusts 25-30 kt decreasing after sunset. 78 && .PRELIMINARY POINT TEMPS/POPS... PDT 57 35 62 39 / 20 0 0 0 ALW 60 38 64 42 / 20 0 0 0 PSC 66 40 71 45 / 0 0 0 0 YKM 63 36 72 42 / 0 0 0 0 HRI 63 38 68 41 / 10 0 0 0 ELN 58 37 69 42 / 0 0 0 0 RDM 52 27 60 33 / 10 0 0 0 LGD 51 32 57 37 / 40 0 0 0 GCD 47 30 58 32 / 30 10 0 0 DLS 60 40 70 45 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory until noon PDT today for ORZ502-509. WA...Winter Weather Advisory until noon PDT today for WAZ030. Wind Advisory until 11 PM PDT this evening for WAZ026. && $$ MORNING UPDATE...83 SHORT TERM...85 LONG TERM....78 AVIATION...78